The present invention relates to ring and pin type cone synchronizers employed for matching the speed of rotation of drive elements employed in a power transmission and particularly relates to changeable ratio power transmissions employed in vehicle drive trains. The synchronizer of the present invention is particularly applicable to heavy duty transmissions for trucks and off-highway vehicles where the axial force required to activate synchronization of the power elements to be engaged, is relatively high. This condition arises particularly in heavy duty truck transmissions where the cone angle of the annular tapered synchronizing surface is a relatively small angle and a substantial wedging effect is created due to the low cone angle of the synchronizing surfaces. The aforesaid wedging affect, although producing a mechanical advantage for actuation of the synchronizer for matching the relative speeds of rotation of the members during engagement, often results in axial locking of the synchronizer ring in such a manner as to prevent unblocking of the sliding clutch which further prevents axial movement when it is desired to move along the synchronizer pins and complete engagement of the power driving elements.
It has thus long been desired to find a way or means of providing for low force synchronization of relative rotation of power drive elements in a power transmission for ease of engagement during ratio change yet to prevent jamming or lockup of the synchronizer which makes it difficult to complete engagement after synchronization has been completed.